For the nonrising stem design, the valve disk is threaded internally and mates with the stem threads. Control valves are also a necessary part of a typical pneumatic system.Chell manufacture Ultra Fine Needle Valves for pressure and vacuum applications, offering very fine and repeatable flow control. Hydraulic valves are very heavy duty valves used to control the fluids either they are highly pressurized or required different flowing directions. Valves are often used to contain dangerous liquids or gases—maybe toxic chemicals, flammable petroleum, high-pressure